Aircraft positioning systems may provide a location of an aircraft (manned or unmanned) system in terms of either an absolute position or a relative position (e.g., relative to other aircraft, communication towers, or the like). However, modern positioning systems such as a Global Navigation Satellite System (GNSS) receiver, while precise, may negatively impact the size, weight, power, and cost (SWAP-C) metrics of smaller, unmanned, or more mission-restricted aircraft systems. In particular, compact aircraft such as unmanned aircraft systems (UAS), balloons, gliders, or light sport aircraft (LSA) may be unable to support GNSS-based hardware, e.g., due to design restrictions or insufficient resources.
Multilateration (MLAT) is an exemplary positioning technique that may be used to determine the location of an aircraft based on signals received from additional proximate aircraft. MLAT is a technique for locating an object based on the time difference of arrival (TDoA) of multiple synchronized signals. In general, MLAT may be used for either navigation or surveillance purposes. As a surveillance technique, for example, TDoA measurements of a signal originating at a single emitter (e.g. an aircraft) and received by multiple spatially separated receiving stations may be used to determine the location of the emitter. As a navigation technique, TDoA measurements of multiple synchronized signals originating from multiple spatially separated transmission sources (e.g. nearby aircraft) and received by a single receiver may be used to determine the location of the receiver.
Automatic dependent surveillance broadcast (ADS-B) signals may provide an exemplary set of signals for determining the location of a vehicle (e.g. a UAS) using alternative positioning systems such as MLAT. ADS-B is a surveillance technology in which ADS-B compliant vehicles determine their positions via satellite navigation (e.g. a GNSS) and broadcast their positions such that ground stations and/or other vehicles may receive the signals. In addition to position information, ADS-B signals transmitted by aircraft include additional information such as the accuracy at which the position of the aircraft is known. Further, in the United States, all aircraft operating in airspace classes A, B, C, and E will be required to be equipped with equipment to transmit ADS-B information. Similar requirements are being implemented globally such that the number of ADS-B compliant aircraft will continue to increase.